Corrosion of Fe-(9~37) wt. %Cr Alloys at 700–800 °C in (N2, H2O, H2S)-Mixed Gas

Fe-(9, 19, 28, 37) wt. %Cr alloys were corroded at 700 and 800 °C for 70 h under 1 atm of N2, 1 atm of N2/3.2%H2O mixed gas, and 1 atm of N2/3.1%H2O/2.42%H2S mixed gas. In this gas composition order, the corrosion rate of Fe-9Cr alloy rapidly increased. Fe-9Cr alloy was always non-protective. In contrast, Fe-(19, 28, 37) wt. %Cr alloys were protective in N2 and N2/3.2%H2O mixed gas because of the formation of the Cr2O3 layer. They, however, became nonprotective in N2/3.1%H2O/2.42%H2S mixed gas because sulfidation dominated to form the outer FeS layer and the inner Cr2S3 layer containing some FeCr2S4